<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div></div>
  </body>
  <style>
    div {
      width: 0;
      height: 0;
      border: 30px solid transparent;
      border-bottom: 30px solid black;
      border-top: 0px;
      border-left: 0px;
    }
  </style>
</html>
